Intercommunication system



July 23, 1940. R. HELMERT INTERGOMMUNICATION SYSTEM Filed July 29, 1939 N /nventor'f Fok/I Hel/nerf HIlor/Jgf.

mentes July za, i940 2,203,923v

UNITED STATES PATENT OFFICE;

` 2.20am i INTEBCOMMUNICATION SYSTEM Robert Helmert, Berlin, Germany, allignor to C. Lorenz Aktiengesellschaft, Berlin-Tempelhoi', Germany, a company Application July'29, 1939, Serial No. 287,198 In Germany August 3, 1938 4 Claims. (Ol. 179-4) This invention relates to intercommunicacoming frequencies of different kind the relays tlon systems, and more particularly to signaling just mentioned are caused to release when the arrangements in telephone systems in which sucontact or armature of the receiving relay is set pervisory signals, such as call signals, disconnect to the opposite side.

5 signals and the like, are transmitted by alter- It is still a further object of this invention to 5 nating currents of dierent audio frequencies. provldemeans for transmitting two different su- It is a known expedient to effect supervisory pervisory signals and to so arrange the receivsignal transmission over telephone lines by a1- ing apparatus that the armature of the receiving ternately transmitting two different frcquenrelay at the end of incoming signals remains in cies in a close succession and to cause the rea given one of its two end positions in order to 10 ceiving apparatus to respond only in cases when selectively control a given one of two dili'erent these signals arrive in a predetermined manner supervisory signals in response to the position in so as to avoid thatl the supervisory signal equipwhich the armature isset. The final position of ment be released by speech currents. the armature at the end of the incoming train In one specic aspect of my invention, the reof different signal frequencies is predetermined 15 ceiving equipment of a telephone or other interby causing one of these frequencies to persist communication system is so arranged that the for a predetermined interval of time at the end armature of the receiving relay in either of its of the alternating signal train. two positions operates an auxiliary relay, and My invention Will be more fully understood these two` auxiliary relays are arranged to confrom the foloWing deseliption taken in eonillnotrol a further auxiliary relay which is slow to tion With` the accompanying drawing, which di- `operate, agrammatically shows one embodiment of my According to a further object of this invention, invention. the further auxiliary relay is caused to release Referring to the drawing, the Operation of the when the two rst-mentioned relays are con- System iS performed as follows: When the subtinually operated, means being provided to mainscriber at the standard central battery telephone tain each one of said two relays operated during apparatus T removes his handset. the double the intervals in which the armature of the rewound relay J is caused t0 operate by current ceiving relay establishes an operating circuit for through both the windings I and II in Series the other of said two auxiliary relays. With apparatus T. The relay R which in a conao In accordance with still a further feature of dition of rest is energized over the Winding II Athis invention the release time of the two rstof relay S and the back-Contact i2 becomes dementioned auxiliary relays is determined by a energized, S0 that after some delay this relay condenser connected across the junctionl point will shift its contact rl and r2 to the released of the said relays with their respective contact portion Shown in the drawing. Before this ocof the armature of the receiving relay in such ours. however, the Winding I of relay S receives manner that the charge currents from this conan alternating Current of say 50 Cycles from the denser involves an additional excitation of the generator G3 over the Contact rl and the contwo auxiliary relays mentioned. tact i2. The contact s of relay S is thus caused According to a further aspect of my invention, to vibrate in rhythm With the frequency of the the velocity with which the two frequencies congenerator G3 so as to alternately Switch the stituting a supervisory signal are alternately audio frequency generators GI and G2 in circuit. impressed upon the line corresponds to the high- 'I'he different frequencies from these two audio est speed of response of the receiving relay of frequency generators are transmitted over transthe signal receiving apparatus. It is thus pos.. former Trl, the line a2b2 and the transformer sible to so time the further auxiliary relay that TT2 to the tuned amplifiers and reotiers Fl and it will release and thus cause the indication of F2 so that the two windings of the receiving rea supervisory signal only when the frequencies lay E are intermittently energized with the reincoming from a signal transmitting apparatus sult that the armature e oscillates so as to al- 50 are intermittently transmitted with a given ternately energize the relays A and B. The conspeed of alteration, lsince at a higher speed'of denser C3 shunted vacross* the .two contacts'vbealteration. the relay is incapable of following tween which the armature e of the receiving relay this higher speed so that one only of the two E vibratesis so dimensioned that the charge currst-mentioned relays is caused to attract, while rent at 50 cycles is suincient to maintain the 55 at a lower speed of alteration between the inrelays A or B energized during the short inter- 55 yaloftime at which the armature e is connected to the other of the said relays. When the two relays A and B are simultaneously energized, a

relay H is short-circuited 'by the contacts a2 and' b2 of the relays A and B, respectively. The relay H reverts its contacts so that the relay D is energiaed over the contact h3.

Y When the relay R ofthe transmitting sidereleases after'some delay. the winding `I of the relay S is Vso energized by the direct current flow through the relay Z that the contact s of relay S remains in the position shown in the drawing.I

thus maintaining the audio frequency generator Gi connected in circuit. Thus. the relay A in the receiving position remains energized due to the energization of the upper winding of the receiving relay E, while the relay B is caused to deenergze. The short-circuit across the relay IHv This indicating lamp may be extinguished by insetting the plug St into `the jack Kl. The energizing .circuit for the relays N4 and G remains established over the contact g after the release of the relay D.

The disconnection'oi' the generator Gi and the switching-through of the speech line at the transmitting'position is effected by the slow-tooperate relay Z. a

The speech currents cannot cause the relay H of the receiving apparatus to release since it must be considered impossible that the two frequencies to which the devices FI and F2 are tuned will alternately arrive at a frequency of 50 cycles during a time which will suilice to simultaneously energize the two relays A and B and thus to cause the release of the relay H.

When the subscriber at the telephone station- T again restores the handset, the relay J releases. The contacts of this relay are restored to normal so that the winding 1I of the relay S now receives an alternating current of 50 cycles from the generator G3. The devices Fl and F2 of the receiving apparatus are thus alternately rendered effective in response to the alternate effectiveness of the audio frequency generators Gi and G11 of the transmitting station when the contact s of relay S oscillatesin rhythm with the 50-cyc1e alternating current from generator G3. 'I'he movement of the armature e of the receiving relay E causes the two relays vl'i and B to operate so that their contacts a2 and b2, respectively,A establish a short-circuit across the relay H which latter releases so as vto revert its contacts. The relay D is therefore energized over the contact h3. When the relay Z of the transmitting apparatus releases after some delay, the winding II of relay S is so energized over' the winding of relay R that the contact s remains in a position in which the audio frequency generator G2 is connected in circuit with the result that the relay A of the receiving apparatus releases while the corresponding relay B remains attracted. 'I'he short-circuit across the relay H is thus removed so that this relay operates whereupon the energizing circuit for the relays G and N is interlrupted, while the relay D still remains operated.

aaoaaas The relay N releases so that the indicating lamp SL announcing the disconnect signal is lighted.

'Ihisindicatinglampmaybeextintuished by re to influence the relay E of the receiving apparatus overa transmission line over which telegraph signais also transmitted. The single dinerence between the telegraph sianal and the signal which is intended to control the action of the relay H is that the frequency transmitted by the generator G3 of the transmitting station is higher than the maximum speed of telegraph signal transmission. The condenser C3 and the relays A and B are so dimensioned that the relays A and B release during the interruptions or spaces between two -signals and during signal, respectively.

It is also possible to cause the generator G3 of the transmitting apparatus to transmit a frequency which corresponds to the speed of telegraphic signals provided that the telegraph transmission yis so arranged that at given time intervals, e. g. at the end of each character a longer pause is inserted between the telegraph signals and provided that the release time of the relay H is so dimensioned that it is longer than the total time of a signal transmitted between two such pauses.

What is claimed is:

1. In an electric communication system, supervisory Signal receiving equipment which is adapted to indicate supervisory signals composed of alternating currents of diiferent frequencies transmitted with a given relation to each other and which comprises a polarized receiving relay adapted to move its armature in response to alternating currents of different frequencies constituting the said supervisory signals, two auxiliary relays adapted to be alternately energized in response to the instantaneous position of the said armature, and a third auxiliary relay for releasing supervisory Signals in response to the simultaneous energization of the said two auxiliary relays.

2. In an electric cummunication system as dened in claim 1, in which means are provided to eifect two different supervisory signal indications. each dependent upon the nal position of the said armature at the end of incoming signaling currents.

3. In an electric communication system as defined in claim 1, in which means are provided to indicate a supervisory call signal when the said armature remains in one end position at the conclusion of incoming signal currents, and to indicate a disconnect supervisory signal when the said armature `remains in its opposite position at the end of incoming supervisory signaling currents.

4. In an electric cummunication system according to claim 1, in which means are provided which in response to the correct incoming frequency maintain the one of the said auxiliary relays operated during the interval of time during which the said armature is connected to the 10 other of the said two relays.

ROBERT HEIMERT. 

